1. Field of the Invention
The present disclosure relates to image processing apparatuses and imaging apparatuses for combining a plurality of frames in alignment processing.
2. Description of the Related Art
In video recording with a digital camera or a digital video camera that serves as an imaging apparatus, there is a method of performing automatic focus processing by aligning image positions to correct an image blur at the frame rate when recording the images, and performing a focus detection evaluation with the aligned image. In such a method, it is not possible to perform the image blur correction processing within the time which is shorter than the frame rate time when recording the images. Consequently, high-frequency components in the spatial frequencies of the object image are lost, and therefore the high-accuracy focus detection evaluation may not be performed.
To ensure the high-frequency spatial frequency components by shortening the image blur time period, there is a method of ensuring an image signal capable of performing the high-accuracy focus detection evaluation by performing an alignment combining process of images obtained by shortening the frame length. In such a method, if the obtained images are used as recording images, the sharpness of the images in one frame can be increased.
However, the method visually emphasizes the image changes between previous and subsequent frames of a captured and recorded image. As a result, the changes in the object discretely (digitally) appear, and this causes unnatural images, which is problematic.
As an example of the combination of image signals, Japanese Patent Application Laid-Open No. 2006-261929 discusses a method of adding a plurality of vertical direction pixels or horizontal direction pixels to use the resultant for a focus detection evaluation.
The control method discussed in Japanese Patent Application Laid-Open No. 2006-261929 is, however, for simply adding the simultaneously generated image signals to ensure the luminance level. Consequently, the control method disclosed in Japanese Patent Application Laid-Open No. 2006-261929 is a control method for performing image blur correction, and the method is not a control method for performing a focus detection evaluation using high-frequency components of an object image. As a result, in the control method discussed in Japanese Patent Application Laid-Open No. 2006-261929, accurate focus detection cannot be performed.